A challenge in building a scalable local advertising platform is to efficiently serve local adverts that are close to a particular physical location. The number of local adverts in the system may be on the order of billions and the physical location distribution of local ads can very skewed or otherwise unevenly distributed, with a large portion of ads residing in several densely populated regions. Difficulties arise in efficiently creating a local ads serving system because of these geographic non-uniformities.
The challenges of building a distributed indexing solution that works on billions of data points across multiple systems therefore poses unique and complex challenges.